1. Field of the Invention
The invention disclosed herein relates to an improved windshield wiper assembly and specifically to a wiper assembly which permits the rotation of the blade in accordance with the direction of movement of the assembly with respect to the windshield, thus increasing the life of the blade and the effectiveness of same.
2. Overview of Prior Art
Since the invention of the automobile windshield, the difficulty of keeping it clean has challenged inventors and engineers. The windshield is of little use if the driver cannot see through it. Even minimal obstructions such as streaks and smears from inadequate wiper blades can result in detrimental and even potentially fatal consequences. The problem with most wiper blades is that they are not used for a long period of time and then when they are needed, they are necessary immediately. For this reason the process of improving the effectiveness and life of the blade is of valued importance. Many attempts have been made to try to accomplish this but have met with only limited success. Many times other problems have been created in the process.
Allowing the blade to rotate axially along the long axis of the blade allows the cleaning edge of the blade to be pulled across the surface instead of pushed. Methods to accomplish this have been disclosed by Cayan in U.S. Pat. No. 5,325,563 and von Meltzing et. al. in U.S. Pat. No. 5,033,157 in which complicated mechanisms and complex part assemblies are used.
These are not only unusually expensive to produce and therefore potentially price themselves out of the market, but the added assembly and small components create a potential for premature deterioration of the structure.
Speth and Quinian et. al. in U.S. Pat. Nos. 4,287,634 and 3,751,754 respectively disclosed similar methods of allowing the blade to rotate along the long axis of the blade. Both provide a pin which extends through an oversized slot. The pin allows axial movement until the pin contacts the edge of the slot, thus halting the movement. The necessity of excessive clearance between moving parts of a device open to the environment is a potential for disaster as liar as debris clogging up the mating components and preventing movement. When this happens the device ceases to function in the desired manner. In addition, the constant "clinking" of the pin against the slot edge every time the wiper blade changes direction is enough to cause the driver and any passengers sitting nearby great irritation. No spring mechanism is used to cause the device to seek a center position perpendicular to the windshield position. This could accomplish the same thing without the sloppy clinking of metal pans.
In U.S. Pat. No. 3,006,014, Krohm disclosed a rotating device that is set on an angle to the wiper arm and does allow for rotation along the long axis of the blade. The purpose is to allow the blade to remain perpendicular to the curved windshield. Though a potentially superior bearing surface is provided as compared to the previously mentioned two patents, the device also does not provide a spring mechanism and therefore the device will operate in a loose and sloppy manner, irritating to the operator of the vehicle on which the device is being used.
A more complicated version of the devices previously mentioned is disclosed by Zaiger in U.S. Pat. No. 2,942,288. In this a separate link is received by the primary yoke that allows for rotation therewith. The manner of rotation is again a pin which extends through an oversized hole or slot. The same problems are provided by this design as with those previously discussed in addition to an additional arm that must be manufactured and assembled. The clinking with the operation of the device is consistent with those previously discussed.
This issue of noise due to the adjoining arm and yoke was addressed by Stratton et al. in U.S. Pat. No. 4,793,020 by providing a cushion therein. The cushion disclosed in the form of a tape is intended as an insulation only. No articulation method such as a pivot pin or similar devices are used that would provide a method of allowing the blade to rotate along the long axis of the blade.
Numerous other devices have been disclosed that address the issue of complying to the curved surface of the windshield, such as that by Lukaszewski in U.S. Pat. No. 5,136,749. In this patent, a primary yoke and a secondary yoke are used thereby providing an increased number of points of force application to the blade toward the windshield. The limitation of these devices is that they do not address the associated wear problems and lack of adequate cleaning when the blade is pushed across the surface of the windshield and not pulled, which can be solved by allowing the blade to rotate. To provide proper function of the blade assembly the combination of increased articulation and rotation must be employed.